Rats and islands. nowadays, the black rat (Rattus rattus) is by far the most widespread terrestrial vertebrate species in Mediterranean islands

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4 Rats and islands nowadays, the black rat (Rattus rattus) is by far the most widespread terrestrial vertebrate species in Mediterranean islands there are only two islands larger than 10 ha without rats (Pianosa Tremiti, 13 ha and Toro, 12 ha), both very distant from mainland (10 km and 33 km) black rat populations may have a detrimental impact on nesting seabirds

5 Why eradicate rats? Shearwaters reproductive in relation to rat presence/absence reproductive success (%) number of nests absent rats present Median 25%-75% Non-Outlier Range rats present sampled rats absent successful Calonectris diomedea (n=661) Data from: La Scola, Zannone, Linosa, Cerboli, Argentarola Puffinus yelkouan (n=31) Data from: Tavolara, Montecristo

6 How eradicate rats? rodenticide and bait: brodifacoum 0.005% in extruded bait blocks bait stations, fixed to trees, shrubs or other substrata average bait station density: 4/ha (1 bs each 50 m)

7 Zannone

8 Where the little money available should be invested? Given that there never will be enough money to restore each valuable able ecosystem, it is necessary to establish some conservation priorities (e.g. Wilson et al., 2006, 2007; Pressey et al., 2007; Howald et al., 2007) Up today, priorities have been mainly established relying only upon u biological value of target communities (i.e. number and diversity y of endemic species, population size, etc.). Monetary costs of the actions have been rarely considered to establish priorities (e.g. see Naidoo et al., 2006; Murdoch et al., 2007)

9 Why considering costs? San Pietro Costs of protecting 1 pair 3,500 3,000 2,500 2,000 P. yelkouan nesting 1,500 population: 500 pairs 1,000 island surface: 5089 ha Molara Molara 3,049 P. yelkouan nesting population: 425 pairs island surface: 348 ha S. Pietro

10 Aims of this study to establish a priority list of Italian islands candidate for rat eradication, relying on both effectiveness and cost/effectiveness criteria to identify the islands which can be more easily recolonized by rats, excluding them for not wasting money to evaluate alternative strategies for islands in which eradication is judged not feasible to compare the return of the investment deriving from adopting a cost-effectiveness or an effectiveness ranking

11 Which islands have the priority? To rank islands for priority of rat eradication, we used Cost-Effectiveness Analysis (CEA) It is a tool used to compare different management alternatives when w the benefits cannot be easily estimated in monetary terms, but the costs c of implementation can be estimated. Computionally,, the COST-EFFECTIVENESS RATIOS (CER) for each island must be computed: Cost : Effectiveness = CER

12 Target species Species 1: Yelkouan shearwater Puffinus yelkouan Italian pop pairs Present in 27 islands Rat-free population: 1 pair > 50% of global population Species 2: Cory s shearwater Calonectris diomedea Italian pop pairs Present in 52 islands Rat-free population: pairs 20% of Medit. population

13 Estimating effectiveness Species 1: Yelkouan shearwater Puffinus yelkouan Species 2: Cory s shearwater Calonectris diomedea Step 1 (island population species1 : Italian pop. sp1) * (island population species1 : regional pop. sp1)/number of regions hosting species1*100 : number of colonies of species 1 = effectiveness for species 1. national importance regional importance rarity Step 2 effectiveness for species 2 (index for species1 + index for species2) * 100 = effectiveness for the island x

14 Estimating costs We estimated analytically costs of rat eradication on each islands, by the following parameters: 4 bait applications for each island 1.6 kg of bait (extruded blocks, active ingredient: brodifacoum 0.005%) per bait station bait station density: islands up to 20 ha: 12 bait stations/ha islands up to 50 ha: 8 bait stations/ha islands larger than 50 ha: 4 bait stations/ha labour costs: islands up to 20 ha: 270 /day travelling expenses: 100 /day opening tracks in shrub vegetation: 110 /ha, applied to on average 1/3 of island surface bait station placing: 40 bait stations/man/day bait station checking and bait replacement: 60 bait stations/man/day

15 Computing Cost-Effectiveness ratio Cost / Effectiveness Ratio (CER) for each island: predicted costs : effectiveness

16 EffectivenessCost-effectiveness ranking ranking Rank Rank Island Island Region Area (ha) P. yelkouan C. diomedea 1 TAVOLARA SAN NICOLA Apulia 46, LINOSA TAVOLARA Sardinia 602, LAMPEDUSA SCOLA Tuscany 1, MONTECRISTO PAN DI ZUCCHERO Sardinia 4, SAN LINOSA PIETRO Sicily 545, SAN PALMAROLA NICOLA Latium 125, MOLARA CARPA Sardinia 0, SAN SAN DOMINO Apulia 208, CAPRAIA VENTOTENE Latium 143, PALMAROLA MOLARA Sardinia 347, PANTELLERIA FORADADA Sardinia 5, PONZA FIGAROLO Sardinia 22, VENTOTENE CAPRARA Apulia 49, PIANA LEVANZO DI ALGHERO Sardinia 13, MONTECRISTO CAPRARA Tuscany 1071, SANTO GIANNUTRI STEFANO Latium 31, PAN DI CAMERE ZUCCHERO W Sardinia 3, LA CAMERE SCOLA E Sardinia 4, ZANNONE BARRETTINI Sardinia 10, MARETTIMO LAMPEDUSA Sicily 2059,

17 Accounting for the risk of rat reinvasion Rats can reinvade islands by swimming or by passive transport on boats English name: Black rat, Roof rat Between 2001 and 2006, we observed black rat recolonization of 4 islands distant between 200 and 382 m from rat-inhabited islands or mainland and SHIP RAT! La Scola Pianosa: 242 m!

18 How many islands are at risk of rat reinvasion? our database includes 308 islands in Italy (surface ha) only 64 (20.8%) host shearwater colonies rats are present in 58 of them number of islands seabirds and rats harbour distance < 500 m combined no yes

19 Cost-effectiveness ranking Rank Island Region Area (ha) P. yelkouan C. diomedea 1 SAN NICOLA Apulia 46, TAVOLARA Sardinia 602, LA SCOLA Tuscany 1, PAN DI ZUCCHERO Sardinia 4, LINOSA Sicily 545, PALMAROLA Latium 125, CARPA Sardinia 0, SAN DOMINO Apulia 208, VENTOTENE Latium 143, MOLARA Sardinia 347, FORADADA Sardinia 5, FIGAROLO Sardinia 22, CAPRARA Apulia 49, PIANA DI ALGHERO Sardinia 13, MONTECRISTO Tuscany 1071, SANTO STEFANO Latium 31, CAMERE W Sardinia 3, CAMERE E Sardinia 4, BARRETTINI Sardinia 10, LAMPEDUSA Sicily 2059,

20 Ranking with islands at high risk of recolonization Isola Regione Area (ha) Berta minore Berta maggiore 1 SAN NICOLA Puglia 46, TAVOLARA Sardegna 602, LA SCOLA Toscana 1, PAN DI ZUCCHERO Sardegna 4, LINOSA Sicilia 545, PALMAROLA Lazio 125, CARPA Sardegna 0, SAN DOMINO Puglia 208, VENTOTENE Lazio 143, MOLARA Sardegna 347, FORADADA Sardegna 5, FIGAROLO Sardegna 22, CAPRARA Puglia 49, PIANA DI ALGHERO Sardegna 13, MONTECRISTO Toscana 1071, SANTO STEFANO Lazio 31, CAMERE W Sardegna 3, CAMERE E Sardegna 4, BARRETTINI Sardegna 10, LAMPEDUSA Sicilia 2059,

21 Ranking without islands at high risk of recolonization Isola Region Area (ha) Yelkouan shearwater Cory s shearwater 1 TAVOLARA Sardinia 602, PALMAROLA Latium 125, BARRETTINI Sardinia 10, MONTECRISTO Tuscany 1071, GIANNUTRI Tuscany 239, ZANNONE Latium 104, SANTO STEFANO Latium 31, MOLARA Sardinia 347, MORTORIO Sardinia 55, LA VACCA Sardinia 9, ROSSA DI TEULADA Sardinia 10, SPARGI Sardinia 421, SERPENTARA Sardinia 31, CAVOLI Sardinia 42,

22 What to do in islands at risk of recolonization? ? 30 no yes harbour distance < 500 m combined

23 If eradication can be performed simultaneously on each island, the group can be recovered S. Maria group (14 islands, 5 with shearwaters) No harbour 50 m 300 m 350 m Option 1: recovering groups of islands

24 Ranking with groups (cost/effectiveness) Rank Island Region Area (ha) P. yelkouan C. diomedea 1 TAVOLARA Sardinia 602, PALMAROLA Latium 125, BARRETTINI Sardinia 10, MONTECRISTO Tuscany 1071, GIANNUTRI Tuscany 239, ZANNONE Latium 104, Soffi group Sardina 4 islands SANTO STEFANO Latium 31, MOLARA Sardinia 347, MORTORIO Sardinia 55, LA VACCA Sardinia 9, S. Maria group Sardinia 14 islands Pianosa group Tuscany 2 islands ROSSA DI TEULADA Sardinia 10, SPARGI Sardinia 421, SERPENTARA Sardinia 31, CAVOLI Sardinia 42, Corcelli group Sardinia 3 islands

25 Option 2: setting prophylaxis depending on risk Gavi 400 m 300 m 200 m 131 m Swimming distance Ponza

26 Option 3: local control (or containing) Zannone

27 Effectiveness vs Cost/effectiveness pairs protected x rank effectiveness cost/effectiveness T-test paired samples: P<0.01

28 Conclusions and perspectives cost-effectiveness ranking differed substantially from effectivess ranking cost-effectiveness ranking allowed an higher return of the investment than effectiveness ranking since several important islands were excluded from the ranking, different approaches should be considered in order to protect important colonies a future development of the model may include a priority list for the Mediterranean

29 Thanks for your attention! Thanks to: N. Baccetti, P. Sposimo, S. Zerunian, A. Perfetti, F. Giannini, F. Corbi, B. Massa and many others!